The present invention is generally related to telecommunications switches, and more particularly to high reliability telecommunications switches employing redundant control systems.
Telecommunications switches facilitate routing and transmission of data in telecommunications networks. Such switches typically include a plurality of Input/Output ("I/O") cards which are interconnected through a switch fabric card. In particular, the switch fabric interconnects each I/O card with every other I/O card such that a data unit received at any I/O card can be transmitted to any other I/O card in the switch.
In addition to interconnecting the I/O cards, the switch fabric may function to control timing operations within the switch and allocate bandwidth to connections through the I/O cards such that collisions are avoided. Such functionality is relatively complex to implement, and consequently switch fabric cards in a telecommunications switch are prone to failure. In particular, control functions that are heavily software dependent are prone to failure due to software bugs. Such bugs may be triggered by specific sequences of events so the card can at times be restored through a reset operation. However, data can be lost in such a reset operation.
To avoid data loss and switch failure due to a switch fabric card failure it is known to employ redundant switch fabric cards. In particular, it is known to install a plurality of switch fabric cards in a single switch so that a standby switch fabric card can be employed in the event that the active switch fabric card fails. However, switch fabric cards are generally high cost items and it is therefore common practice to install only one standby switch fabric card, which may not provide sufficient reliability.